2. Cambridge, Mass., the difference in time being 4 hr. 44 min. 30 sec.

3. Canton, China, the difference in time being 7 hr. 33 min. 6 sec.

4. Manila, P. I., the difference in time being 8 hr. 3 min. 52.4 sec.

5. Quebec, Can., the difference in time being 4 hr. 44 min. 52 sec.

6. Tokyo, Japan, the difference in time being 9 hr. 18 min. 58 sec.

Written Exercise

246. Illustrative Example (2). At Para, Brazil, a watch that keeps Paris time is 3 hr. 23 min. 20.9 sec. fast. What is the longitude of Para?

WORK

15° 15′ 15′′

3 23 20.9 50° 50' 13"

2 20 22 48° 29′ 51′′

EXPLANATION.

The difference in longitude is 50°

50' 13'. But the watch is fast and Para is in West longitude, while Paris is in East longitude. So we subtract the Paris longitude from the difference.

Ans. The longitude of Para is 48° 29′ 51′′ west.

1. The time of two ships, A and B, at sea differs by 3 hr. 20 min. What is the difference in their longitude? If the longitude of A is 45° 30' east and her time is later than B's, what is B's longitude?

2. It is 5 o'clock 15 min. P.M. at a certain place named X, and 8 P.M. at another place named Y. Which place is further east? and how much?

3. At noon at Liverpool 2 persons land from different steamers. The watch of each has the time of the place he came from. By one it is 9 o'clock 50 min. P.M., by the other 8 o'clock 10 min. A.M. Give the direction whence each came. Find the difference in longitude of the two places..

4. Explain how news from London dated 8.30 P.M. can be received in New York at 3.30 P.M. the same day.

5. A ship sails from longitude 42° 10' 15" west to longitude 20° 4' 16" east. What change should a passenger make in his

watch?

6. At 2.30 P.M. a ship in longitude 30° 20′ 15′′ west sends a wireless message to another ship. It is received at 2 P.M. What is the longitude of the receiving ship?

7. At 9 o'clock A. M. a steamer in longitude 50° 10' 15"west sends a wireless telegram to the Nantucket light-ship 70° west longitude. What is the time of receiving it at the light-ship?

NOTE. Sailing westward around the earth, a ship gains 1 da. on the sun; sailing eastward, it loses 1 da. To adjust its calendar, at an irregular line called the international date line, corresponding to the 180th meridian, it carries its date forward 1 da. if going westward, and back 1 da. if going eastward.

STANDARD TIME

247. In 1883 the railroads in the United States and Canada. decided to run their trains by the time of the five meridians 15° apart, the 60th, 75th, 90th, 105th, and 120th. Time belts extending, nominally, 71° on each side of these several meridians, use each the same time. This is called standard time.

The map on p. 166 shows the time belts in the United States. The irregularities are due to each railroad's selecting the most convenient stations on its road for changing from the standard time of one belt to that of the other.

248. By standard time, the belt that has the time of the 60th meridian is called the Atlantic time belt, the others in order from east to west are the Eastern, the Central, the Mountain, and the Pacific.

Eastern time is exactly 1 hour earlier than Atlantic time, Central time 1 hour earlier than Eastern time, Mountain time 1 hour earlier than Central time, and Pacific time 1 hour earlier than Mountain time.

Standard time has been adopted by most civilized countries, the time meridian chosen being, usually, some multiple of 15 from the prime meridian of Greenwich.

249. 1. The stock quotations in New York were telegraphed from that city to Chicago, San Francisco, Boston, Denver, and New Orleans at 10.30 A.M. standard time. Allowing no time for this transmission, give the time the telegram reached each city.

2. Allow 30 min. for transmission, and tell the time when a dispatch sent at 8 A.M. standard time in San Francisco reaches St. Louis, Philadelphia, Washington, Portland, Me.

3. At 2.15 P.M. St. Paul time, give the time at Baltimore, Quebec, Galveston, Los Angeles.

4. Find the difference in standard and solar time at Chicago; at San Francisco.

250. The shortest distance between points is a straight line. Two or more lines that have the same direction are called parallel lines.

The outside of anything is called its surface.

A flat surface is called a plane.

The representation of a plane surface bounded by lines is called a plane figure.

The sum of the bounding lines of a plane surface is called its perimeter.

Written Exercise

251. 1. 1 mile equals how many rods? how many yards? how many feet?

2. Change .25 mile to rods; 59.4 in. to rods.

3. At what rate per minute does a train go, if it runs 35 mi. per hour?

4. Measure the length of each side of your schoolroom and find the perimeter of the floor surface.

5. Find the distance around the schoolhouse lot in rods and feet.

6. What is the cost of 18 yd. of rubber hose at 163¢ a foot? 7. The two parallel sides of Mr. Vernon's house lot are 57 yd. 2 ft. apart. Give the width of the lot in feet.

8. What is the cost of netting for the two ends of a tennis court measuring 18 yd. each, at $.15 per running foot?

9. How many steps of 2 ft. 6 in. does a person take in walking 31.2 miles ?

10. Mt. St. Elias is 3 mi. 2184 ft. high. Give its height in feet.

11. Mt. Blanc lacks 96 ft. of being 3 mi. high. Pike's Peak is 1633 ft. lower than Mt. Blanc. How high is Pike's

Peak?

252. The difference in direction of two lines that meet, or tend to meet, is called an angle. The lines are called the sides and their meeting point the vertex of the angle.

021

081

130

a

10 30

091

b

PROTRACTOR

C

d

To measure angles we use a protractor, which is a half circle whose circumference is marked off into 180°, and each degree into 60' (Art. 213). Any part of the circumference of the circle is called an arc.

The arc cd on the protractor is 30°, so the angle of the lines bd and be, whose vertex is at the center of the circle, is 30°. The arc ad is 50°, and so the angle of the lines ab and bd, which is read angle abd, is 50°.

An angle of 90° is called a right angle.

TWO RIGHT ANGLES

Any angle less than 90° is called an acute angle.
Any angle greater than 90° is called an obtuse angle.

Oral Exercise

253. 1. Repeat the table for Angles and Circles, Art. 213.

2. In the protractor above, what kind of angle is angle abc? angle abe? angle cbd? angle cbe?

3. What kind of angle do the hour and minute hands of the clock form at 9 o'clock? at 10 o'clock? at 5 o'clock? at 8 o'clock? at 7 o'clock?

4. Through how many degrees does the hour hand of the clock move in 6 hr. ? in 3 hr.? in 1 hr.? in 90 min.? in 1 hr.? in 12 hr.?

5. The hour and minute hands of a clock form an angle of how many degrees at 3 o'clock ? at 2 o'clock? at 1 o'clock ? at 1:30 o'clock?